For many millennia, man has experimented with various metals and obtained more and more high-strength alloys from them. For this, a variety of chemical elements were used. The Bronze Age is an era during which an alloy of tin and copper (CuSn6) became popular. What is this material and why was it so popular?
History of Bronze Age
Thanks to the improvement in the processing of metals such as copper and tin, in 3000 BC. the Bronze Age began. It is characterized by the active production of such an alloy as bronze, which was used to make tools and jewelry.
In the modern metallurgical industry, in addition to copper and tin, materials such as aluminum, phosphorus, lead, and zinc are also used. The name itself comes from the Persian word "berenj", which translates to "copper".
It is known that the first bronze was made from Cu and arsenic and was called arsenic. However, due to its toxicity, it very quicklychanged to pewter. Not surprisingly, blacksmiths were often depicted as ugly and mutilated. In fact, it was. Prolonged contact with arsenic had a very bad effect on their body. For this reason, an alloy of copper and tin is called bronze, since it is these components that are most often present in it.
Characteristic of bronze
We all know that a metal like copper is very soft, ductile and absolutely fragile. At the same time, it has a very high electrical and thermal conductivity. An alloy of tin and copper is a material that significantly exceeds the characteristics of these chemical elements separately. In other words, bronze has high hardness, strength, but at the same time it is quite fusible.
The discovery of this alloy played a big role in the metallurgical industry. Despite the fact that many other materials were later invented, even today it is very popular due to its good mechanical properties.
The ability of bronze to resist corrosion
One of the most important properties of an alloy is its corrosion resistance. This is especially true for those compositions in which there is a significant content of manganese and silicon (more than 2%).
It has been found that bronze exhibits high corrosion resistance in contact with water (marine and fresh water), concentrated alkalis and acids, light metal sulfates and chlorides, and dry gases (tinless bronzes).
Of course, in gener althe corrosion properties of the alloy depend on the alloying elements. Thus, a high lead content reduces the ability to resist corrosion, while nickel increases this property.
Types of bronze
Alloying elements that may be in the composition of this alloy can significantly change its properties, and the type of bronze also depends on them. In addition, tin can be replaced by other elements. For example, BrAMTS-7-1 can be deciphered as follows: 92% copper, 7% aluminum, 1% manganese. This brand of bronze does not contain tin and due to this it has a high resistance to alternating load. It is used to make bolts, screws, nuts and parts for hydraulic installations.
Another example is tin foundry bronze of the brand BrO10S10. It contains up to 83% copper, 9% tin, 8% lead and up to 0.1% iron, silicon, phosphorus and aluminum. It is designed for parts that operate under high specific pressures, such as plain bearings.
Despite the fact that bronze is an alloy of tin and copper, in some cases, such a chemical element as Sn is not used. Another example of tinless bronze is heat-resistant. For its manufacture, only copper 98-99% and cadmium 1-2% are used. An example is the brand BrKd1. It is a heat-resistant cadmium bronze with high heat resistance and electrical conductivity. It can be used for the manufacture of parts of resistance welding machines, collectors of electric motors and other parts operating at high temperatures and requiring goodconductivity.
Another type of alloy used to make gaskets in automotive bearings and bushings is pressure-machined tin bronze. An alloy of copper and tin contains such alloying elements as lead (4%), zinc (4%), aluminum (0.002%), iron (0.005%). The steel grade is called BrOTsS4-4-4. It is thanks to the percentage of these chemical elements that this alloy can be processed by pressure and cutting. The color of bronze also depends on impurities. So, the less copper the alloy contains, the less pronounced the color: more than 90% - red, up to 80% - yellow, less than 35% - gray-steel.
Bronze working
As mentioned earlier, an alloy of tin and copper is a fairly durable material. It is difficult to sharpen, cut and work with pressure. In general, this is a casting material with low shrinkage - about one percent. And even despite the low fluidity and tendency to segregation, bronze is used for the manufacture of castings with complex configurations. Art casting is no exception.
Alloying elements that are added to an alloy of tin and copper improve its properties and reduce the price. So, for example, alloying with lead and phosphorus improves the processing of bronze, and zinc increases its corrosion resistance. For certain purposes, deformed alloys are made. They easily change their appearance when using cold forging.
Scope of application
Of course, the use of bronze does not lose its popularity in our time. Souvenirproducts, decorative interior items, decorations for gates and wickets … In addition, the alloy is used for the manufacture of fittings (handles, hinges, locks) and plumbing fixtures (faucets, fittings, gaskets, faucets). In industrial areas, bronze also has extensive areas of use. So, casting alloy is used to make bearings, sealing rings, bushings.
The widespread use of bronze is particularly affected by its corrosive properties. For this reason, it is used for the manufacture of parts of mechanisms that operate in constant contact with water. The high elasticity of the alloy makes it possible to manufacture springs and parts of instrumentation from it.
Smelting Bronze
Of course, each alloy has its pros and cons. Bronze is an alloy that consists of copper and tin, and therefore it perfectly tolerates any remelting. It can be used multiple times for completely different purposes. On the other hand, if the bronze contains a large amount of impurities such as magnesium, silicon, aluminum, then the mechanical properties may decrease during remelting.
This is due to the fact that the alloying elements that improve the characteristics of bronze are oxidized during melting and form refractory oxides, which are located along the boundaries of the crystal lattice. They break the bond between the grains, making the bronze more brittle.
How to distinguish bronze from brass and copper
One of the most common questions is the differencethis alloy from others similar in appearance. Of course, within the industry and with the help of special reagents, this is quite simple. But what if you need to determine the material at home?
Let's start with the fact that the alloy consists of tin and copper. The masses of these substances in percentage can be different. The more copper, the brighter the color will be, but due to the content of tin in the alloy, it will be an order of magnitude heavier than, for example, pure Cu.
If we compare bronze with brass, the latter has a more yellowish tint. Copper itself is very ductile, but alloys based on it are quite elastic and hard. You can also determine which material is in front of you by heating. So, in brass, under the influence of high temperature, zinc oxide is released and the product acquires an ashy “plaque”. But bronze, when heated, will not change its properties.
Artworks
Quite often you can find various bronze figurines and figurines. Many works of art were created in ancient times and in the Middle Ages.
Alloys containing copper and tin are used to make:
- Fences and gates, which are not only incredibly beautiful, but also durable.
- Elements of stair structures.
- Souvenirs and sculptural compositions.
- Decorative lighting fixtures: sconces and chandeliers.
- Items for interior decoration.
In order to piss the necessarycomposition, create a special model of wood, gypsum or polymeric materials - the so-called molding. The cavities of this figure are filled with clay and removed after casting. After manufacturing, the surface can be plated with gold, nickel, chrome or silver.
It is very important to note that, as a rule, an alloy of tin and copper without alloying elements is used to make works of art. This is due to the fact that the more such components are present in bronze, the greater its shrinkage, which negatively affects the quality and shape of the product.
